Three copies of a triangle were rotated and positioned as shown.



Which statement about the figure is always true?




A.
Angle 1, angle 2, and angle 3 form a straight angle.


B.
m∠1 + m∠2 + m∠3 = 360°


C.
The measures of ∠1, ∠2, and ∠3 are all equal.


D.
m∠1 + m∠3 = m∠2